Influenza Rates Head Downward in Early 2022; Flu Season Appears Less Severe Than Anticipated BY NEAL LEARNER
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ontrary to some projections, cases of seasonal influenza peaked at the end of last year and started to decline in early 2022. Some experts had expected a more robust 20212022 flu season in the United States, as COVID-19 pandemic restrictions eased and students headed back to the classrooms. But data so far have not borne that out. Overall, influenza activity has decreased in recent weeks, while sporadic activity continues across the country, and some areas are seeing an increase, the CDC said in its March 18 influenza surveillance report. As of March 12, the CDC estimates 2.9 million flulike illnesses, 28,000 hospitalizations and 1,700 deaths due to influenza this season, with influenza A(H3N2) being the dominant strain. Thirteen deaths were in children, more than last year, but well below pre-COVID seasons. Accompanying the decline in cases was a drop in the percentage of outpatient visits due to respiratory illnesses. Those cases are now below baseline, the agency added. The overall cumulative hospitalization rate this season is 4.4 per 100,000 population. While higher than last year, the current rate is significantly lower than pre–COVID-19 levels. The hospitalization rates ranged from 16.9 to 51.4 per 100,000 people during the seasons from 2016-2017 through 2019-2020, the CDC noted. By Feb. 12, 3% of specimens submitted to clinical laboratories were positive after peaking at 6% earlier in the season, according to Lisa Grohskopf, MD, MPH, of the CDC’s Influenza Division, who updated the Advisory Committee on
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Immunization Practices (ACIP) on Feb. 23. Most specimens that were subtyped were H3N2 viruses, she added, and so far these viruses are “genetically closely related to the vaccine virus, but there are some antigenic differences that have developed as H3N2 viruses continue to evolve,” she explained. The number of B/Victoria viruses is low, and they are antigenically similar to the vaccine. The cumulative hospitalization rate (FluSurv-NET) is higher than that for the entire 2020-2021 season, but lower than that observed at this time during the four seasons preceding the pandemic, she added. The ACIP is reviewing the approved enhanced seasonal influenza vaccines to decide whether to make a recommendation for adults who are 65 years of age and older. At the meeting, the panel acknowledged the benefits of an enhanced influenza vaccine compared with standard egg-based flu shots. Three vaccines are being reviewed: Fluad Quadrivalent (Seqirus), Fluzone (Sanofi Pasteur) and Flublok Quadrivalent (Protein Sciences Corp.). “According to the CDC, older adults have an increased risk of influenza-related complications and severe outcomes. Data from the recent ACIP systematic review support the benefit of an enhanced influenza vaccine for this population,” said Gregg Sylvester, the chief medical officer of Seqirus.
Did COVID-19 Mitigation Help? The numbers are heading in a positive direction, even if the reason isn’t exactly clear. What first looked to be a “moderate or moderately severe” influenza season may be tapering off,
